V

Holography Glossary

Vacuum back - a camera back with a perforated plate through which air is drawn by a pump. A sheet of film is therefore sucked flat against the plate and held firmly during exposure. Used for special large format cameras such as copying devices where dimensional accuracy is critical.

Vacuum easel - a compact printing frame which ensures firm contact between the film and paper by excluding air between the surfaces. Some types are used to hold the paper flat on the enlarger baseboard when enlarging.

Vanishing point - the point at which parallel lines, viewed obliquely, appear to converge in the distance.

Vapor discharge lamp - a lamp in which electrical current passes through a vapor or gas rather than through a wire filament, thus producing illumination.

Veil - a uniformly distributed silver deposit in a photographic image, not forming part of the image itself. Also known as fog.

Video still camera - a camera using an electronic charge coupled device instead of film.

View camera - a large format camera which has a ground glass screen at the image plane for viewing and focusing.

Viewfinder - a system used for composing and sometimes focusing the subject. There are several types: direct vision, optical, ground glass or reflex.

Viewpoint - the position of the camera in relation to the subject.

Vignetting - a printing technique where the edges of the picture are gradually faded out to black or white. It also refers to a fall off in illumination at the edge of an image, such as may be caused by a lens hood or similar attachment partially blocking the field of view of the lens.

Vinyl film - an emulsion coating on a polyvinyl chloride acetate base, with less shrinkage than conventional film bases.

Viscose sponge - a synthetic sponge used to wipe surplus water off films before they are hung up to dry.